The Effect of Probiotics in a Milk Replacer on Leukocyte Differential Counts, Phenotype, and Function in Neonatal Dairy Calves

Probiotics have been investigated for many health benefits; however, few studies have been performed to determine the effects of oral probiotics on peripheral blood and respiratory immune cells in cattle. Our objectives were to determine changes in health and growth status, differential blood cell counts and function, and blood and lung cell function using flow cytometry and PCR in dairy calves fed a milk replacer with (PRO, N = 10) or without (CON, N = 10) the addition of probiotics to the milk replacer and dry rations from birth to weaning. Performance and clinical scores were not different between the treatment groups. Treatment-by-day interactions for peripheral blood leukocyte populations differed in cell number and percentages. A greater percentage of leukocytes expressed the cell surface markers CD3, CD4, CD8, CD11b, and CD205 on d 21 in CON animals. Lung lavages were performed on five animals from each treatment group on d 52. There were no differences between treatment groups for the expression of cytokines and Toll-Like Receptors as measured using Polymerase Chain Reaction, possibly due to the small sample size. Oral probiotics appear to affect peripheral blood immune cells and function. Their effect on overall calf health remains to be determined.

Systematic review of an intervention: the use of probiotics to improve health and productivity of calves

The aims of this study were to undertake a systematic review and meta-analysis of the types of probiotic formulations that are commercially available and to critically appraise the available evidence for the effectiveness of probiotics in improving the health and productivity of calves. Relevant papers were identified to answer the question: 'In calves aged between birth to one year, is the use of probiotics associated with changes in haematological or biochemical parameters, faecal bacteria counts, average daily live weight gain, dry matter intake, or feed conversion ratio?' The search of the literature yielded 67 studies that fit the primary screening criteria. Included studies were assessed for bias and confounding using a predefined risk assessment tool adapted from the Cochrane Collaboration's tool for assessing risk of bias in randomised trials and GRADE guidelines. Meta-analysis was performed using Review Manager and R. Random sequence generation was low in more than 59 % of studies. Risk of allocation concealment and performance bias were largely unclear in over 68 % of studies. Calves fed probiotics had increased average daily live weight gains (ADG) from birth to weaning (mean difference [MD] = 83.14 g/d 95 % CI = 58.36-107.91, P < 0.001) compared with calves on a control diet. Calf age reduced the level of heterogeneity of the effect of probiotics on ADG for calves between one to three weeks of age (τ² = 73.15; I² = 4%; P = 0.40) but not for calves older than three weeks of age (τ² = 2892.91; I² = 73 %; P < 0.001). Feed conversion ratio (FCR) was lower for calves on probiotics (MD = -0.13 kg of dry matter intake (DMI) to kg of live weight (LW) gain, 95 % CI = -0.17 to -0.09, P < 0.001), and the heterogeneity of effect was large in younger aged calves (τ² = 0.05; I² = 78 %; P = 0.03). The risk of bias regarding the methodology in the included studies was high. The quality of evidence for each outcome was categorised as moderate. There is sufficient data to support the effectiveness of probiotic use in some applications such as for the improvement of performance and productivity parameters of calves. However, the evidence is weak for other potential probiotic uses in calves such as improved health and reduced risk of disease. Therefore, the existing data are inconclusive and do not support the use of probiotics as an alternative to antimicrobials to improve calf health and productivity.

Variation in the response of bovine alveolar lavage cells to diverse species of probiotic bacteria

OBJECTIVE

Probiotics are fed to improve enteric health, and they may also affect respiratory immunity through their exposure to the upper respiratory tract upon ingestion. However, their effect on the respiratory system is not known. Our aim was to determine how probiotics affect functions and markers of bronchoalveolar lung lavage cells (BAL) isolated from lungs of calves at slaughter.

RESULTS

Treatments consisted of ten probiotic species and one control treatment. Probiotics and BAL were incubated 1:1 for 2 h at 37 °C and 5% CO₂. The cell surface markers measured included CD14, CD205, and CD18, and E. coli bioparticles were used to measure phagocytosis and oxidative burst. Differences were considered significant at P ≤ 0.05 and were noted for percent cells fluorescing and mean fluorescence intensity for CD14 and CD205. Additionally, oxidative burst was different as measured by both percentage of cells fluorescing and mean fluorescence intensity, and phagocytosis differed among species as measured by mean fluorescence intensity. Overall, probiotic species differed in their ability to suppress or increase leukocyte function showing that probiotic bacteria differentially modulate BAL.

The effect of Enterococcus faecium M74 feed additive on the extended-spectrum beta-lactamases/AmpC-positive Escherichia coli faecal counts in pre-weaned dairy calves

The increasing occurrence of extended-spectrum beta-lactamases and/or AmpC-positive Escherichia coli among different species of food producing animals poses a threat to public health. The animal gut plays a key role in the development of antibiotic resistant bacteria, allowing the selection, multiplication and subsequent contamination of the farm environment. However, applicable procedures for reducing such bacteria on farms are currently unavailable. The present study was aimed to determine whether a probiotic administration to new-born dairy calves would reduce faecal shedding of extended-spectrum beta-lactamases and/or AmpC-positive Escherichia coli during the pre-weaning period. Ten randomly assigned new-born Holstein calves on a dairy farm with recent evidence of high occurrence of AmpC-positive Escherichia coli among calves were treated by a probiotic mix within 12 h after birth. Nine control calves were not treated. Faecal samples were collected from each calf daily on days 2 through 5, and then on days 7, 10, and 14. The faecal samples were cultured, and the mean numbers of cefotaxime-resistant Escherichia coli and confirmed enteroaggregative Escherichia coli were compared between the two groups. Results suggested that the Enterococcus faecium probiotic treatment (Enterococcus faecium M74, NCIMB 11181) of new-born calves did not reduce the enteroaggregative Escherichia coli counts in their faeces. There was no significant difference in the shedding of enteroaggregative Escherichia coli between the probiotic-treated and control calves throughout the two-week study period.